1. Field of the Invention
The present invention relates to liquid sprayers, and more particularly to sprayers of the aspirator type that proportionally mix a liquid with water under pressure and provide a spray of the liquid/water mixture.
2. Description of Related Art
Liquid aspirators are commonly employed to apply diluted solutions containing chemicals such as pesticides, fungicides, herbicides, and fertilizers to lawns or garden foliage. Typically, sprayers of this type are attached to a garden hose and the pressure of the water delivered through the hose is used to create a vacuum that causes a chemical solution in the sprayer to be aspirated into the water in order to provide a diluted solution that is subsequently sprayed.
In general, sprayers of this type include a container for holding the chemical solution to be diluted and sprayed, and a mixing head, the base portion of which serves as a cover for the chemical container. Such mixing heads generally include an adapter for connecting the mixing head to a standard garden hose, and a hand valve for turning on and off the flow of water from the garden hose. The mixing head also includes a venturi chamber in which water from the garden hose is mixed with undiluted chemical solution from the container.
In principle, as water passes through the venturi chamber, a syphoning or vacuum action, is created by virtue of the velocity of the water passing through the chamber, to draw chemical from the container and into the venturi chamber for dilution with water from the garden hose. The basis of operation of these sprayers is Bernoulli's principle.
Many garden sprayers of this type have a fixed, nonadjustable dilution ratio. In such cases, the chemicals to be used must be diluted and premixed with water in the container to provide a proper concentration of chemical in the final water spray.
For example, U.S. Pat. No. 3,770,205 discloses a sprayer wherein a portion of the incoming water is diverted into a chemical container for mixing with chemicals in the container. The mixture is then drawn back into a mixing head for further dilution with the nondiverted portion of incoming water. Although the dilution ratio of the disclosed sprayer is not adjustable, the sprayer includes a rotatable disk that enables the unit to be changed from a "liquid" mode to a "pellet" mode, depending upon whether the chemicals in the container are in liquid or solid form.
A number of commercially available sprayers do provide for multiple dilution ratios. Multiple dilution ratio sprayers typically do not require chemical premixing and directly provide the desired concentration of chemical in the desired spray. These sprayers are more accurate because they eliminate the need for premixing. Furthermore, liquid chemicals in the container which are not used can be saved and returned to the package (can or bottle) containing the original undiluted chemicals.
Multiple dilution ratio sprayers generally provide dilution ratio variation by either selectively proportioning the size of the opening in the passageway that extends from the chemical container to the mixing (venturi) chamber, or by varying the size of an auxiliary air vent opening which bleeds air into the mixing chamber in order to control the level of vacuum and the resulting syphoning action on chemical from the container. In both cases, a multiple orificed selector, such as a rotatable wheel or slidable stem interposed in the passageway or vent, is used to select the desired dilution ratio.
U.S. Pat. Nos. 3,112,884 and 3,191,869, issued to Robert A. Gilmour, disclose spraying devices wherein the dilution ratio of chemical to water is adjusted by bleeding air into the mixing chamber to control the vacuum level therein. In such sprayers, the size of the air vent opening is adjusted to meet the desired dilution ratio, while the size of the aperture through which chemicals flow into the mixing chamber remains constant.
In practice, it has been found that multiple dilution ratio sprayers that control the air vent orifice size to vary the dilution ratio are not as accurate as those which vary accurately the size of the fluid opening between the chemical container and the mixing chamber.
Another problem encountered with prior art sprayers that require adjustment of the air bleeding into the mixing chamber is that they require at least three openings into the mixing chamber: one for the water, one for the chemical, and one for the air.
In other prior art sprayers, such as the one disclosed in U.S. Pat. No. Re 29,405, the dilution ratio is controlled by changing both the diameter of the mixing chamber and the diameter of the opening through which the chemical flows into the mixing chamber. Such diameters can be changed by rotating a drum mounted in the mixing head, in which drum are contained a plurality of passageways of different diameter.
However, the prior art sprayers that control the dilution ratio by varying either the size of the fluid opening or the air vent, are susceptible to clogging caused by chemicals drying in the control orifice or in narrow passages, thus rendering the sprayers inaccurate or inoperable. Such clogging necessitates disassembling the unit to clean the passages and orifices. In some sprayers, it is not a simple task to remove the orifice selector or to disassemble the unit for cleaning.
A third type of sprayer is disclosed in U.S. Pat. No. 4,475,689. That sprayer includes a rotatable disk containing a plurality of apertures of different sizes. Adjacent each aperture is a small cavity that is connected to the aperture through a small channel. The size of each aperture and each cavity is specifically chosen for a particular dilution ratio. In operation, the disk is rotated until the desired aperture and cavity is aligned with the inlet to the mixing chamber. Undiluted water is then admitted into the selected cavity. That water is used to make an initial dilution of the chemical that is eventually drawn into the mixing chamber through the aperture. Subsequent to the initial dilution, the diluted chemical is then drawn into the mixing chamber where it is further diluted with water before being sprayed.
The use of a dilution cavity adjacent the aperture in the rotatable disk creates certain problems. For example, a special "figure eight" shaped sealing ring is necessary to separately seal the dilution cavity from the aperture, and an additional chamber must be provided adjacent the mixing chamber in order to supply fresh water to the dilution cavity prior to the mixture of the diluted chemical into the mixing chamber. Such a system requires numerous small components, and is thus not only difficult to manufacture, but includes many openings and chambers that are prone to clogging. To further complicate matters, many of these openings and chambers are not accessible to a user, and thus may not be easily cleaned or unclogged.
The clogging and cleaning problem associated with lawn and garden sprayers is further aggravated by the fact that such sprayers are typically used infrequently. Thus, if the sprayer is not cleaned promptly after use, the resulting chemicals may build up in the system so that they are likely to solidify and become difficult to clean.